A variable valve timing control device includes a rotation member for opening
or
closing a valve, a rotation transmission member engaged with the rotation member
to be relatively rotatable, a vane provided on either one of the rotation member
or the rotation transmission member, a hydraulic chamber formed between the rotation
member and the rotation transmission member and including an advance angle chamber
and a retarded angle chamber, the advance angle chamber and the retarded angle
chamber being formed by dividing the hydraulic chamber by the vane, a first hydraulic
passage for supplying and discharging a fluid to the advance angle chamber, and
a second hydraulic passage for supplying and discharging the fluid to the retarded
angle chamber. The vane includes a surface hardness determined to be higher than
a surface hardness of a sliding surface of the rotation member or the rotation
transmission member for sliding the vane.
